In integrated circuit technology, it is often required to make or break electrical connections in order to fabricate and/or modify a circuit. For example, in programming logic arrays, certain gates and circuit elements must be connected while others must be isolated. Also, individual memory cells of programmable read only memories can be programmed by selectively connecting and isolating individual cells from certain conducting lines.
Various devices and methods have been developed to cut or fuse a conductor to permanently interrupt its continuity, many of which are applicable for use in integrated circuits. These prior fuses typically include a resistance within the conductive path. By passing a large enough current through the resistive fuse, the fuse is heated to a sufficient level to melt the conductive metal and boil it away. Thus, the continuity of the line is permanently interrupted.
These prior fuse devices have several drawbacks. First, they introduce their own resistance into the conductive path which, depending upon the application, can have an undesirable effect. For example, if the line is to remain intact and continue to be used as a conductor, voltage drop, power dissipation and other resistive effects of the fuse are introduced into the circuit.
Also, access to the fuse to pass a fusing current through it can be difficult. In many of these prior devices, a pair of pointed probes contact opposite sides of the fuse to apply the fusing current. These systems require that the fuse be physically accessible. In addition, the process of precisely locating the probes to blow the fuse can be slow and inefficient.
Other prior fuse devices involve cutting the conductor with a laser. In these devices a laser beam of sufficient power to melt the conductor is directed onto the conductor. This requires that the breakpoint of the conductor be physically accessible to oftentimes bulky laser equipment. Also, once again, precisely locating the laser beam on the conductor can be a slow process.